Spark plug having a reversible inner electrode



April 28, 1970 c. J. KRW 3,509,403

SPARK PLUG HAVING A REVERSIBLE INNER ELECTRODE Filed July 24, 1967 2 Sheets-Sheet 1 I 1 w 77 V \Z y) j f4 ff j,

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SPARK PLUG HAVING A REVERSIBLE INNER ELECTRODE Filed July 24, 1967 2 Sheets-Sheet 2 INVENTOR.

United States Patent O 3,509,403 SPARK PLUG HAVING A REVERSIBLE INNER ELECTRODE Cecil J. Krow, P.0. Box 44, Ralston` Okla. 44650 Filed July 24, 1967, Ser. No. 655,627 Int. Cl. H01t 13/20, 13/22 U.S. Cl. 313-121 11 Claims ABSTRACT OF THE DISCLOSURE A spark plug having tapered inner and outer electrodes, the outer electrode surrounding the inner, and in which the inner, outer or both electrodes are reversible.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to spark plugs for internal combustion engines.

Description of the prior art Prior art spark plugs have an inner electrode comprising a rod supported by a porcelain sleeve and an outer electrode which may be annular and is supported by a body mountable in the engine.

SUMMARY OF THE INVENTION According to the invention, the outer or ground electrode is of annular tapered shape and in most forms of the invention the central or inner electrode also has a slight taper. The porcelain insulator is held in position by a sleeve threaded into the base and the inner electrode is secured within the porcelain insulator by a threaded holder. Either or both of the electrodes may thus be easily removed for cleaning or renewal without removing the base from the cylinder head, despite the formation of carbon deposits during use.

The central electrode holder is preferably of copper and provides substantial heat transfer to the upper section of the porcelain insulator, thus assisting to eliminate cold plug fouling and extreme pre-ignition heat.

The invention therefore provides simple means for reconditioning spark plugs to obtain maximum fuel eiliciency motor performance and long plug life. With the invention, it is possible to choose different lengths for the central and ground electrodes, thus determining the desired operational heat range. The securing means for the electrodes resists loosening from shock or vibration, and the construction reduces the need for expensive heat-resistant electrode metals and machined parts.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a cross-sectional view in elevation of a spark plug incorporating the principles of this invention;

FIGURE 2 is a side elevational view of the central electrode;

FIGURE 3 is a side elevational view, partly sectioned, of the ground electrode and its holder;

FIGURE 4 is a cross-sectional view in elevation of a modified form of the spark plug in which the ground electrode comprises a spiral member;

FIGURE 5 is a side elevational view of the central electrode of the FIGURE 4 spark plug;

FIGURE 6 is a cross-sectional view of the ground electrode;

FIGURE 7 is a fragmentary side elevational view of the high voltage terminal and a retainer for the central electrode;

FIGURE 9 is a cross-sectional view in elevation of another modication of the spark plug in which the ground electrode is slotted to permit adjustment of the spark gap spacing and the central electrode is reversible;

FIGURE 10 is a side elevational view of the reversible central electrode;

FIGURE l1 is a fragmentary side elevational view of the lower portion of the central electrode holder;

FIGURE 12 is a side elevational view of the ground electrode;

FIGURE 13 is a cross-sectional view in elevation of another embodiment of the spark plug which provides a reversible combination porcelain insulator and central electrode;

FIGURE 14 is a side elevational view of the reversible portion of the spark plug, and

FIGURE 15 is a side elevational view of the slotted ground electrode.

DESCRIPTION OF rPHE PREFERRED EMBODIMENTS Referring to the embodiment of FIGURES 1 to 3, the spar-k plug is generally indicated at 11 and comprises a base 12 having a lower threaded end portion 13 adapted to be mounted in a cylinder head of an internal combustion engine. The upper portion of base 12 has a threaded lbore 14 which leads downwardly to a cylindrical bore portion 15 at the lower end of which is a sloping shoulder 16. An inwardly tapered bore 17 extends downwardly from shoulder 16 to another sloping shoulder 18 adjacent the bottom of base 12. A smaller bore 19 extends downwardly from shoulder 18 to the bottom of the base.

A ground electrode 21 of saucer-shaped construction rests on shoulder 18 and partially covers bore 19, this electrode having a central opening 22. A ground electrode holder 23 is disposed in bore 17, this holder having a tapered shape with a flange 24 which rests on shoulder 16. The lower edge of holder 23 engages the outer edge of ground electrode 21 to retain the electrode in position.

A porcelain insulator 25 is provided which retains a central electrode 26. Insulator 25 is of elongated shape, having a cylindrical central portion 27 which is disposed within bore 15 and a lower end 28 which is located within holder 23, but is more sharply tapered than the holder and is spaced inwardly therefrom. The upper portion of insulator 25 is tapered more gradually, and a bushing 29 ts over the insulator and is threaded into portion 14 of the base to hold the insulator in position with portion 27 holding ground electrode holder 23 against shoulder 16. The shoulder 30 at the lower end of insulator portion 27 is so shaped as to engage flange 2-4 in a manner creating a gastight seal. Bushing 29 may have a hexagonal shape for engagement of a tool.

Porcelain insulator 25 has a slightly tapered bore 31 extending through the lower portion thereof, and a wider tapered bore 32 extending through the upper portion thereof, a shoulder 33 being located between these two bores. The upper portion of bore 32 is threaded as indicated at 34.

The central electrode 26 has a central shoulder 35 which rests on shoulder 33 of insulator 25. Shoulder 35 is at the midpoint of electrode 26, and the electrode tapers slightly in both directions from this shoulder, The taper is such that either end of the electrode will fit into tapered bore 31, and the length of each half of the electrode will bring its lower end through opening 22 of ground electrode 21. The spacing between the ground and central electrodes may be chosen of course to suit requirements, but in any case, it will be noted that an annular spark gap is formed between the electrodes.

A central electrode holder 36 is disposed within bore 32 and receives the upper end of electrode 26. Holder 36 is preferably fabricated of copper or a similar material having a high coefiicient of heat conductivity. It therefore serves to rapidly transfer heat from the electrode to the upper section of insulator 25. Holder 36 is tapered to an angle complementary to the taper of bore 32, and the upper portion 37 of the holder is threaded, this thread engaging the internally threaded portion 34 of insulator 25. The taper of holder 36 will assist in overcoming carbon seizure when it is desired to remove the holder. Holder 36 has a tapered central bore 38 for receiving the upper end of electrode 26. The upper end 39 of holder 36 is hexagonally formed, so as to permit engagement by a tool, and is surmounted by a post 41 for receiving the high voltage Wire. Electrode 26 will of course be in close electrical conducting relationship with holder 36, and hexagonal portion 39 will engage the top of porcelain insulator 25.

The central and ground electrodes may be made of various lengths to determine the desired operational heat range of the spark plug. It will be noted that the construction of the spark plug is quite simple, particularly the central section thereof, minimizing the need for screw machine parts and expensive heat resistant electrode metals.

In operation, the shock and vibration to which the spark plug is subjected will not cause loosening or slippage of the parts due to the manner in which they are secured together, particularly the tapered or sloping contact surfaces.

The manner in which holder 36 assists in preventing preignition and plug fouling will now be explained. In a cold running engine hot spark plugs with an iron core work satisfactorily at low speeds but are overheated at high speeds. Deterioration of the tip of the electrode often develops and pre-ignition often appears. In a hot running engine cold iron core plugs run well at high speeds but often foul at low speeds, misring and wasting gas.

With the highly conductive central electrode holder 36 functioning to transfer heat rapidly from electrode 26 to the upper portion of insulator 25, the spark plug is provided with flexibility of function which will permit it to adapt to either extreme heat or cold. At high engine speeds, holder 36 will rapidly transfer heat from the electrode, thus preventing pre-ignition. At low speeds the holder will assist in preventing spark plug fouling and misfire.

To renew or recondition the electrode spark gap area in order to obtain maximum fuel eiciency and long plug life, it is merely necessary to remove either holder 36, bushing 29 or both, depending upon the electrode to be renewed, cleaned, or reversed. More particularly, unthreading of holder 36 will permit the central electrode 26 to be removed either to reverse it, thus doubling its life, or to clean or replace it. To work on the central electrode, bushing 29 need not be disturbed. By removing bushing 29 and extracting insulator 25 and holder 23, access can be gained to ground electrode 21. Note that this will not require removal of holder 36 from insulator 25.

FIGURES 4 to 8 illustrate another embodiment of the invention Which is basically similar to the first embodiment but provides a ground electrode fabricated of a spiral wire. This spark plug is generally indicated at 101 and comprises a base 102, a porcelain insulator 103 and a bushing 104 securing the insulator to the base in the manner previously described. Central electrode 105 in this case is not reversible but has a slight taper to assist removal despite carbon deposits. A holder 106 receives the upper portion of central electrode 105 and is threadably mounted into the upper portion of insulator 103. As in the previous embodiment, holder 106 is preferably fabricated of a material such as copper which will rapidly transfer heat from the central electrode to the upper portion of the insulator. The lower end of electrode 105 projects through an opening 107 in the lower end of insulator 103, and the upper enlarged end 108 of electrode is held against the top of holder 106 by a combined retainer and a high voltage terminal post 109. A flange 111 on holder 106 is crimped over the upper rim of insulator 103 so that removal of electrode 105 may be accomplished merely by unscrewing mmeber 109. For this purpose, this member is provided with a hexagonal tool-engageable surface 112, as seen in FIGURE 7.

The ground electrode 113 in this embodiment comprises a spiral wire which is tapered to fit against the tapered inner wall 114 of base 102. This wire is preferably fabricated of a heat-resistant metal, and it is held in position by engagement of shoulder 115 of insulator 103 with a frustoconical heat sealing gasket 116. The shape of electrode 113 may of course be varied to suit requirements FIGURE 8 illustrates the modiiied construction for the upper portion of the spark plug shown in FIGURES 4 to 7. In this construction, a hexagonal shape 117 is formed on holder 106 immediately above the crimped flange portion 111. This will permit a wrench to be applied to member 106, holding it in position while member 109 is being rotated by engagement of a wrench with its hexagonal portion 112.

FIGURES 9 to 12 illustrate still another embodiment of the invention which difers from that previously described mainly in that the outer electrode is slotted to permit adjustment of its spacing with respect to the central electrode. The spark plug is generally indicated at 201 and comprises a base 202, a porcelain insulator 203 and a bushing 204 which are similar to those previously described. A reversible central electrode 206 'is provided, this electrode being held by a holder 207 which is threadably mounted to the upper portion of insulator 203. As in the previous embodiments, holder 207 may be fabricated of copper so as to quickly transfer heat from electrode 206 to the upper portion of the insulator.

Electrode 206 in this case is relatively small compared with electrode 26, and its upper portion ts into a slotted lower portion 208 of holder 207. This slotted holder end will permit easy removal and replacement or reversal of the electrode. As in the previous embodiments, the parts are tapered so as to assist in removal despite carbon deposits.

Ground electrode 209 is shaped somewhat similarly to the combined shape of ground electrode 21 and its holder 23 in the embodiments of FIGURES 1 to 3. That is, it is a one-piece electrode which will be retained in a tapered ibore 211 in base 202. Circumferentially spaced slots 212 extend upwardly from the lower opening 213 of electrode 209 which surrounds central electrode 206. These slots will permit bending of electrode 209 to a certain extent to adjust the spark gap.

FIGURES 13 to l5 illustrate another embodiment of the invention which differs from the previous embodiments mainly in that the central electrode is permanently mounted in the porcelain insulator, the latter being reversible to reverse the central electrode. 'Ihe spark plug is generally indicated at 301 and comprises a base 302 with a lower externally threaded portion 303 to be mounted in the cylinder head. A spacer 304 is mounted on portion 303 and may be of any desired thickness depending upon the desired operational heat range of the plug. A ground electrode 305 is mounted within a tapered bore 306 in case 302. This electrode is shaped somewhat similarly to electrode 209 of the previous embodiment in that it is of tapered shape and has a slotted lower portion surrounding the central electrode.

The central electrode is indicated at 307 and extends entirely through a double-conically shaped porcelain insulator 308. This insulator has a central cylindrical portion 309 with sloping upper and lower shoulders 311 and 312 respectively. Portion 309 of the insulator is disposed within a cylindrical bore 313 of the base and the upper shoulder 311 is engaged by a bushing 314 threaded into the top of the base to hold the insulator in position. The lower shoulder 312 of the insulator portion 309 engages the upper flange of ground electrode 305.

Electrode 307 extends outwardly from both narrow ends of insulator 308. With the angles of shoulders 311 and 312 equal, and the surfaces on bushing 314 and electrode 30S which engage them also being equal, both ends of the central electrode may be used by merely removing bushing 31'4 and turning over porcelain insulator 308. In either case, the upper end of electrode 307 will be used for the high voltage terminal connection.

While it will be apparent that the exemplary embodiments herein illustrated are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A spark plug comprising a base adapted to be mounted in a cylinder head, an annular outer ground electrode having at least a major portion thereof disposed within a bore in said base, an elongated insulator having a relatively wide portion disposed in said bore, means removably securing said insulator in said bore whereby the insulator holds said ground electrode in said bore so as to create a gas-tight seal, a bore in said insulator, an inner electrode within said lastmentioned bore, said inner electrode having a tapered shape with its narrow end protruding from said insulator and disposed within said annular ground electrode, the tapered shape of said an inner electrode within said last-mentioned bore, said despite carbon deposits, and an inner electrode holder fabricated of material having a high coeflicient of heat conductivity engageable with said inner electrode and removably mounted in the portion of said insulator remote from said base so as to be in good thermally conductive relation therewith, thereby serving to rapidly transfer heat from said inner electrode to said remote portion of `the insulator.

2. The combination according to claim 1, said holder having a tapered screw connection with said portion of the insulator, thereby facilitating the removal of said holder from said insulator despite carbon deposits.

3. The combination according to claim 1, the bore of said base being tapered, said ground electrode being complementarily tapered whereby removal thereof is facilitated despite carbon deposits.

4. The combination according to claim 1, said inner electrode holder having a portion projecting outwardly from said insulator, an upper enlarged end on said inner electrode and means attached to said projecting end of the inner electrode holder for connection of a high voltage wire, said last-mentioned means also holding the enlarged end of said inner electrode against the top of said holder.

5. The combination according to claim 1, the bore in said vbase being tapered, said ground electrode comprising an annular member at the lower end of said bore, and a ground electrode holder within said bore having a taper complementary thereto.

6. The combination according to claim 1, the bore in said base being tapered, said ground electrode comprising a spiral wire having a taper complementary to that of said base bore.

7. The combination according to claim 1, the bore in said base being tapered, said ground electrode comprising an annular member tting within and having a taper complementary to that of said base bore, and axially extending slots at the narrower end of said ground electrode which permit bending of the ground electrode to adjust the spark gap.

8. The combination according to claim 7, the wider end of said ground electrode having a ange engageable by said insulator to create said gas-tight seal.

9. The combination according to claim 1, said inner electrode having a wider central portion at the wider end of said taper and another tapered portion extending in the opposite direction symmetrical with said rst tapered portion, the second tapered portion being removably disposed within said holder, the holder having a tapered bore to receive said second tapered inner electrode portion, whereby the inner electrode may be withdrawn from said holder and reversed to dispose the second tapered portion within said annular ground electrode.

10. The combination according to claim 9, said inner electrode holder having axial slots adjacent the portion receiving said second tapered inner electrode portion t0 facilitate removal thereof.

11. A spark plug comprising a base adapted to be mounted in a cylinder head, an outer ground electrode carried by said base, an elongated insulator having a relatively wide portion disposed in said bore, means removably securing said insulator in said Ibore whereby the insulator holds said ground electrode in said bore so as to create a gas-tight seal, a bore in said insulator, an inner electrode within said last-mentioned bore, said inner electrode having a tapered shape with its narrow end protruding from said insulator and disposed within said ground electrode, and :its wide end protruding from said bore, the tapered shape of said inner electrode facilitating its removal from said insulator despite carbon deposits, an inner electrode holder fabricated of material having a high coeicient of heat conductivity engageable with said inner electrode and removably mounted in the portion of said insulator remote from said base so as to be in good thermally conductive relation therewith, thereby serving to rapidly transfer heat from said inner electrode to said remote portion of the insulator, an enlarged portion at the wide end of said inner electrode resting on a portion of said inner electrode which protrudes from said insulator, and a member threaded on said protruding end of the inner electrode holder to retain said enlarged portion of the inner electrode and to serve as a connection for a high voltage wire.

References Cited UNITED STATES PATENTS 1,091,451 3/1914 Bullock 313-141 1,271,620 7/1918 Schmidt 313-145 X 1,348,913 8/1920 Welch 313-125 X 1,488,526 4/1924 Butler 313-122 X 1,648,770 11/1927 Jacobs 313-122 1,946,809 2/1934 Pillman 313-121 1,959,639 5/1934 Paulson 313-125 X 2,017,364 10/1935 Anderson 313-122 X 2,048,481 7/1936 Arnois 313-122 X 2,060,340 11/1936` OMarra 313-122 FOREIGN PATENTS 1,007,312 2/ 1952 France.

JAMES W. LAWRENCE, Primary Examiner E. R. LA ROCHE, Assistant Examiner U.S. Cl. X.R. 313-122, 141 

